This invention relates to a method of preparing ceramic materials with reduced carbon levels. More specifically this invention relates to a method of preparing ceramic materials with reduced carbon levels by pyrolyzing silicon-containing preceramic polymers in the presence of ammonia. This invention also relates to a method of preparing ceramic materials with controlled carbon levels.
Ceramic materials have been prepared from many different silicon-containing preceramic polymers. For example, polycarbosilanes, polysilazanes, polysilanes, organosilsesquioxane-containing sol-gels, and organopolysiloxanes have been used as preceramic polymers to prepare ceramic materials. The ceramic materials were prepared by heating the silicon-containing preceramic polymers to elevated temperatures under an inert atmosphere. The ceramic materials so prepared contained significant amounts of carbon. Such carbon is probably in the form of both silicon carbide and free carbon.
It would be desirable to obtain ceramic materials from silicon-containing preceramic polymers where the resulting ceramic materials contain controlled and limited amounts of carbon. It would also be desirable to obtain essentially carbon free ceramic materials from such silicon-containing preceramic polymers. It is an object of this invention to provide a method by which ceramic materials may be obtained from silicon-containing preceramic polymers where the resulting ceramic materials contain reduced but controlled amounts of carbon. It is another object of this invention to provide a method by which ceramic materials may be obtained from silicon-containing preceramic polymers where the resulting materials are essentially carbon free. Still other objects will be apparent from a consideration of this specification.